1. Field of the Invention
This invention relates to solids handling, and more particularly to apparatus for introducing particulate solids into the bottom of a solids upflow vessel, such as a vertical solids upflow retort used for heat treating oil-producing or oil-containing solids to recover oil and/or gas therefrom.
2. Description of the Prior Art
The problem of transporting particulate solids from a solids feed supply, such as a bin or reservoir of the particulate solids, into the bottom of a solids upflow vessel has been encountered in diverse operations, exemplary of which are the feeding of oil-producing and/or gas-producing solids, such as oil shale, tar sand, bituminous coal, oil-saturated diatomaceous earth, and the like into the bottom of a vertical solids upflow retort for treating the solids to recover oil and/or gas therefrom, and the production of synthesis gas by the reaction of gas containing steam with carbonaceous solids such as coal, coke, and the like.
In these operations, difficulties are encountered in the design and operation of mechanical feed systems because of the nature of the particulate solids being transported, typical solids being abrasive and difficult to handle on the one hand and on the other being friable and tending to abrade, thereby forming large quantities of undesirable fine particles. Feeder devices used to introduce solids into the bottom of an upflow solids bed must move the solids against the weight of the solids bed. Also, it is often the case that the solids must be transported from a storage bin at atmospheric pressure into a solids upflow vessel which operates at a superatmospheric pressure. These factors, coupled with the often gigantic size of the equipment required to obtain the desired solids feed capacity, and the fact that in some applications the feeder device must operate at elevated temperatures and in contact with liquids and/or gases produced in the solids treating process, produce difficult design problems involving large and complex mechanical forces and complicated mechanical loadings that must be adequately provided for in the feeder design.
A number of different apparatus and methods for introducing particulate solids into the bottom of a solids upflow vessel have been proposed. U.S. Pat. Nos. 2,501,153 to Berg, 2,640,014 to Berg, 2,875,137 to Lieffers et al. and 2,895,884 to Switzer disclose solids feeding apparatus and methods in which particulate oil shale is introduced upwardly into the bottom of a vertical retort by means of a piston reciprocating in a feed cylinder that is oscillated between an outlet of a shale feed reservoir and the bottom solids inlet of the retort. While such oscillating feeder apparatus can be satisfactorily employed to introduce particulate solids into a solids upflow vessel, a number of problems and limitations are encountered when using such feeders in large capacity commercial units, such as oil shale retorts having capacities on the order of 10,000 tons of oil shale per day or more. Specifically, oscillating feeder apparatus having these capacities are extremely large and require substantial clearance between the supporting foundation and the bottom of the retort, increasing the height and cost of the retort structure. The clearance between the arcuate seal plates oscillated with the feed cylinder and the bottoms of the feed reservoir and retort must be extremely small, such as about 0.030 to 0.060-inch. Machining of these parts to such close tolerances is very difficult and at best is very costly. Furthermore, it is difficult to completely fill the feed cylinder when it is in the inclined or canted position and, therefore, these oscillating cylinder feeders have a reduced volumetric efficiency.
Various other solids feeder systems have been proposed, exemplary of which are those described in U.S. Pat. Nos. 300,385 to Mathieu, 2,029,760 to Derby et al. and 2,871,170 to Bewley et al. German Patent 144,436 discloses a manually operated device for stoking a boiler with coal which includes a piston-containing cylinder into which the coal is loaded and a lever mechanism for moving the cylinder horizontally into position below the fire box and driving the piston upwardly to force the coal into the bottom of a bed of burning coal. While this device may have application in firing small boilers it is wholly unsuited for feeding particulate solids into the bottom of a large capacity solids upflow vessel, which may be operated at superatmospheric pressure.
U.S. Pat. Nos. 4,033,467 to Bewley et al. and 4,037,736 to Pownall et al. disclose solids feeding apparatus and methods in which particulate solids are introduced upwardly into the bottom of a vertical solids upflow vessel by means of twin pistons reciprocating in twin feed cylinders that are rotated and reciprocated, respectively, between one or more solids feed chutes and the bottom solids inlet of the solids upflow vessel. While such feeders can be satisfactorily employed to introduce particulate solids into a solids upflow vessel at very high rates, the mechanical complexity and enormous size of these feeders results in a very high cost of construction and relatively high operating expense. The Pownall et al. feeder carriage is supported by complex roller bearing-type roller wheel assemblies engaging four structural rails mounted under the carriage, the feed cylinders and the piston actuating hydraulic cylinders. When used for the retorting of oil shale or the like, fine particulate matter settling to the bottom of the feeder housing may cause excessive wear on the rails and roller wheel assemblies. Also, the complex roller wheel assemblies of the Pownall et al. feeder present difficult roller wheel alignment problems. Thus, a need exists for an effective and less mechanically complex apparatus for introducing particulate solids into a solids upflow vessel at high rates which avoids the foregoing problems.
Accordingly, it is a primary object of this invention to provide an improved apparatus for introducing particulate solids upwardly into the bottom of a solids upflow vessel.
Another object of this invention is to provide a mechanically simple and effective solids feeding apparatus having lower construction and operating costs than the prior art apparatus.
Yet another object of this invention is to provide a solids feeding apparatus in which the volume of the feeder housing encasing the apparatus is reduced.
Still another object of this invention is to provide a solids feeding apparatus in which the exposure of the movable weight-supportive elements of the apparatus to particulate fines is reduced so as to minimize wear on such elements.
A further object of this invention is to provide a solids feeding apparatus and method which is relatively simple mechanically so as to reduce the problems of precisely positioning the feeder mechanism.
A still further object of this invention is to provide a solids feeding apparatus and method in which the moving parts thereof are relatively easily accessible for maintenance and repair.
Yet another object of this invention is to provide a solids feeding apparatus and method in which the forces applied to the particulated solids being handled are reduced to a practical minimum.
Additional objects, advantages and features of the invention will become apparent to those skilled in the art from the following description when taken in conjunction with the accompanying drawings.